34 PROCEEDINGS OP THE AMERICAN ACADEMY 



morbid growth starts up in the cells surrounding them. The 

 cavity in which the spermogonium is forming enlarges very much 

 as the hyphae continue to grow and fill it. This enlargement takes 

 place chiefly in a vertical direction, although there is a consider- 

 able lateral expansion as well, as the spermogonium rises above the 

 surrounding epidermis. The shape finally assumed is that of an 

 inverted truncated cone, but at times the spermogonia are almost 

 pyriform. No differentiation of the hyphae into anything like a 

 peridium is seen, the cell walls of the host plant remaining as the 

 only covering that the spermogonium has even to maturity. Event- 

 ually the upper wall disappears, being apparently absorbed and 

 finally broken through by the hyphae beneath, which are thus ex- 

 posed to the air. The abnormal growth that affects the cells in 

 which the spermogonium is developing is also taken up by the epi- 

 dermal cells which immediately surround it. These increase some- 

 what in diameter, but chiefly extend themselves in height, and, 

 owing to the excessive development of the top of the spermogonium, 

 are often somewhat bent upon themselves. On one side they cling 

 fast to the spermogonium wall, on the other they are rounded off, 

 rising considerably above the other epidermal cells (Figs. 5, 6). 

 These cells serve the purpose of supporting the spermogonium, the 

 ring of them completely surrounding it, as is shown in the figure of 

 the transverse horizontal section (Fig. 7). Usually a second row 

 of cells, outside of the supporting cells, are also modified to some 

 extent, and serve in turn to support the inner row. In some cases 

 it was observed that a third row of cells was also somewhat dis- 

 torted, and in leaves which were very thickly beset with spermo- 

 gonia scarcely an epidermal cell was not to some extent swollen. 



The further development of the spermogonium is not of especial 

 interest in this connection. As it matures, it gradually takes on 

 the characteristic orange color of these organs, and the hyphae are 

 seen to become slightly swollen at the tips. From the tips of 

 the hyphae the spermatia are abstricted, to be finally liberated by 

 the breaking away of the enveloping cell wall (Fig. 8). It is not 

 infrequently the case that a large number of spermatia are formed 

 before being set free (Fig. 5). The color of the spermogonium is 

 due, as in other Uredineae, to the bright orange oil-like particles 

 which are found in the hyphae. In addition to the oil globules, 

 the hyphae are filled with finely granular matter which also has 

 an orange tinge. The contents of the surrounding epidermal cells 

 are greatly altered, varying from an orange to a brownish yellow 



